This condition first appeared in a conjecture of Dahlberg, where it arose via a specific change of variables (REF ) introduced by Dahlberg, Kenig-Stein, and by Nečas
([1]}, [2]}). This change of variable is relevant to the study of smooth equations in Lipschitz domains. In particular, an example of an operator satisfying the above Carleson condition is the divergence
form operator generated from the pull-back of the Laplacian under the change of variable in (REF ).
